Coated cemented carbide cutting tool member and process for producing the same

ABSTRACT

The present invention relates to a coated cemented carbide cutting tool member, which includes:  
     a substrate and a hard coating layer deposited on the substrate, wherein the hard coating layer has an average thickness of 3 to 25 μm and includes:  
     (1) at least one layer having an average thickness of 0.1 to 5 μm and including a granular Ti compound selected from the group including TiC, TiN, TiCN, Ti 2 O 3 , TiCO, TiNO, TiCNO and mixtures thereof;  
     (2) a TiCN layer having an average thickness is 2 to 15 μm and including a lo longitudinal growth crystal structure; and  
     (3) an Al 2 O 3  layer having an average thickness of 0.5 to 8 μm;  
     wherein the TiCN layer includes a growth direction and a compositional gradient of carbon and nitrogen along the growth direction. The invention also relates to a process for producing a coated carbide member, which includes depositing a TiCN layer with a reactive gas, the layer having a lower portion and an upper portion; and, during the depositing, changing a concentration in the reactive gas of at least one selected from the group including CH 3 CN,CH 4 ,N 2 , and mixtures thereof; wherein the depositing of the lower portion is carried out at a deposition temperature of 850-950° C., and the depositing of the upper portion is carried out at a deposition temperature of 960-1040° C. The invention also provides a coated carbide member produced by the above-noted process. By use of the present invention, a coated carbide member is provided that resists chipping of cutting edge over long periods of time even when used for high speed, high feed, and thick depth-of-cut interrupted cutting operations of steels and cast irons.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a coated cemented carbidecutting tool member (hereinafter referred as “coated carbide member”)that resists breakage and chipping of its cutting edge for a long periodof time, particularly when it is applied to cutting operations ofextremely severe conditions such as high speed, high feed, thickdepth-of-cut interrupted cutting of steels and cast irons.

[0003] 2. Description of the Related Art

[0004] Coated carbide members are widely used in various fields ofcutting operations, for example, continuous and interrupted cuttingoperation of metal work pieces such as steels and cast irons. Coatedcarbide members are typically manufactured by depositing a hard coatinglayer having an average thickness of 3 to 25 μm and including (a) atleast one titanium compound layer having an average thickness of 0.1 to5 μm and composed of at least one layer of granular titanium compoundselected from titanium carbide (hereinafter referred to as “TiC”),titanium nitride (TiN), titanium carbonitride (TiCN), titanium oxide(Ti₂O₃), titanium carboxide (TiCO), titanium nitroxide (TiNO) andtitanium carbonitroxide (TiCNO), (b) TiCN layer having longitudinalgrowth crystal structure (1-TiCN) with its average thickness of 2 to 15μm, and (c) aluminum oxide (Al₂O₃) layer having an average thickness of0.5 to 8 μm, on tungsten carbide-based cemented carbide substrate. Thecommon technique for depositing hard coating layer includes CVD(Chemical Vapor Deposition) and/or PVD (Physical Vapor Deposition).

[0005] Al₂O₃ has several different crystal polymorphs, among which thealpha-Al₂O₃ is known as thermodynamically the most stable polymorphhaving corundum structure, and typical polymorphs of Al₂O₃ used as ahard coating layer are stable alpha-Al₂O₃ and metastable kappa-Al₂O₃.1-TiCN layer is manufactured by the CVD method at moderate temperaturessuch as 700 to 950° using a reaction gas mixture, which includes organiccyanide compounds such as acetonitrile (CH₃CN), such as disclosed inJapanese Unexamined Patent Publication No.6-8010 and No.7-328808.

[0006] In recent years, there has been an increasing demand for cuttingoperations that save labor and time. Accordingly, the conditions underwhich the cutting operation takes place have become more severe, i.e.,high speed, high feed and thick depth-of-cut. With regard toconventional coated carbide members, the 1-TiCN layer found inconventional hard coating layers has fairly good toughness itself, andconsequently the whole hard coating layer also shows sufficienttoughness. Thus, the conventional hard coating layer exhibits excellentcutting performance without any chipping at cutting edge duringcontinuous high speed cutting operations. When subjected to extremelysevere cutting conditions (e.g., high speed, high feed and thickdepth-of-cut interrupted cutting), however, the cutting edge ofconventional hard coating layers are subject to chipping because ofinsufficient toughness, and, consequently, the tool lifetime becomesshorter.

SUMMARY OF THE INVENTION

[0007] Accordingly, one object of the present invention is to provide acoated carbide member that resists chipping of cutting edge over longperiods of time even when used for high speed, high feed, and thickdepth-of-cut interrupted cutting operations of steels and cast irons.

[0008] This and other objects have been attained by the presentinvention, the first embodiment of which provides a coated cementedcarbide cutting tool member, which includes:

[0009] a substrate and a hard coating layer deposited on the substrate,wherein the hard coating layer has an average thickness of 3 to 25 μmand includes:

[0010] (1) at least one layer having an average thickness of 0.1 to 5 μmand including a granular Ti compound selected from the group includingTiC, TiN, TiCN, Ti₂O₃, TiCO, TiNO, TiCNO and mixtures thereof;

[0011] (2) a TiCN layer having an average thickness is 2 to 15 μm andincluding a longitudinal growth crystal structure; and

[0012] (3) an Al₂O₃ layer having an average thickness of 0.5 to 8 μm;

[0013] wherein the TiCN layer includes a growth direction and acompositional gradient of carbon and nitrogen along the growthdirection.

[0014] Another embodiment of the present invention is a process forproducing a coated carbide member, which includes:

[0015] depositing a TiCN layer with a reactive gas, the layer having alower portion and an upper portion; and

[0016] during the depositing, changing a concentration in the reactivegas of at least one selected from the group including CH₃CN,CH₄,N₂, andmixtures thereof; wherein

[0017] the depositing of the lower portion is carried out at adeposition temperature of 850-950° C., and the depositing of the upperportion is carried out at a deposition temperature of 960-1040° C.

[0018] Another embodiment of the invention provides a coated carbidemember, produced by the above-noted process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Various other objects, features and attendant advantages of thepresent invention will be more fully appreciated as the same becomesbetter understood from the following detailed description of thepreferred embodiments of the invention.

[0020] The present invention is particularly suitable for providing ahard coating layer that is coated on the cutting member of a cuttingtool. The term “cutting member” refers to the part of the cutting toolthat actually cuts the work piece. Cutting members preferably includeexchangeable cutting inserts which are mounted on the bit holders ofturning tools, face milling cutter bodies, and end-milling cutterbodies. Cutting members also preferably include the cutting blade ofdrills and end-mills. The cutting member is preferably made of tungstencarbide-based cemented carbide substrates.

[0021] The order of depositing the layers (1-3) is not particularlylimited, and more than one of each layer may be deposited, so long as atleast one of each layer is present.

[0022] Preferably, the hard coating layer is deposited on the substrateby chemical vapor deposition and/or physical vapor deposition.

[0023] The hard coating layer preferably coats a portion of the surface,more preferably the entire surface of the cutting member. The hardcoating layer preferably includes (a) at least one titanium compoundlayer composed of at least one layer of granular titanium compoundselected from TiC, TiN, TiCN, Ti₂O₃, TiCO, TiNO and TiCNO, (b) 1-TiCNlayer having a compositional gradient of C and N along with its growthdirection, and expressed as TiC_(1-x)N_(x), wherein x ranges from 0.45to 0.95 at top portion, and it ranges from 0.05 to 0.40 at bottomportion, and (c) Al₂O₃ layer.

[0024] Preferably, the growth direction of the (gradient) TiCN layer isfrom the surface on which the TiCN layer is deposited, and the terms“upper” or “top” portion and “lower” or “bottom” portion are withrespect to the surface on which the TiCN layer is deposited; the loweror bottom portions being deposited first, and the upper or top portionsbeing deposited on the lower or bottom portion. The TiCN layer may bepreferably deposited on the substrate, or may also preferably bedeposited on one or more intervening layers.

[0025] The present invention is particularly suitable for coated carbidemember having a long lifetime and whose hard coating layer has excellenttoughness characteristics. The present inventors have found:

[0026] (A) Continuous or periodical changes of the gas concentration ofthe reactive gas component such as CH₃CN,CH₄ and/or N₂ during thedeposition of 1-TiCN layer gives 1-TiCN layer that has a compositionalgradient of C and N along with its grown direction, and preferably theconcentration of C decreases and that of N increases from bottom to topin that layer. This gradient 1-TiCN layer is preferably expressed bymolecular formula TiC_(1-x)N_(x,)wherein x is the atomic ratio of N tothe sum of C and N and it ranges from 0.45 to 0.95 at top portion of thegradient 1-TiCN layer and ranges from 0.05 to 0.40 at bottom portion ofit. The concentration gradient from bottom portion to top portion mayvary continuously or step by step, owing to its manufacturing gascondition.

[0027] Preferably, the deposition temperature is changed from 850-950°C. for the bottom portion to 960-1040° C. for the top portion togetherwith the change in gas concentration mentioned above, in terms of givinga more favorable crystal structure of the gradient 1-TiCN layer. Morepreferably, the bottom portion is deposited at a deposition temperatureof 875-925° C., most preferably 885-900°C. More preferably, the topportion is deposited at a deposition temperature of 980-1020° C., mostpreferably 990-1010°C.

[0028] (B) The gradient 1-TiCN layer according to the invention hasexcellent toughness compared to conventional 1-TiCN layer manufacturedby CVD method at moderate temperature range such as 700 to 950° C.without any compositional gradient. Therefore, in the coated carbidemember that includes the gradient 1-TiCN layer according to the presentinvention as a constituent of hard coating layer, the hard coating layeritself desirably exhibits excellent toughness and imparts excellent longtool lifetimes without any chipping at the cutting edge, even when it isapplied to extremely severe cutting operations such as high speed, highfeed, and thick depth-of-cut interrupted cutting of steels and castirons.

[0029] The present invention provides for a coated carbide member thatexhibits superior resistance against chipping at cutting edge for a longperiod of time even when it is applied to extremely severe cuttingoperations such as high speed, high feed, and thick depth-of-cutinterrupted cutting of steels and cast irons, because of excellenttoughness of the hard coating layer, by providing a coated carbidemember preferably composed of a cemented carbide substrate and a hardcoating layer preferably having an average thickness of 3 to 25 μmformed on the substrate by means of CVD and/or PVD method, and thatcomprise (a) at least one titanium compound layer having averagethickness of 0.1 to 5 μm and composed of at least one layer of granulartitanium compound selected from TiC, TiN, TiCN, Ti₂O₃, TiCO, TiNO andTiCNO, (b) 1-TiCN layer that has compositional gradient of C and N alongits growth direction having average thickness of 2 to 15 μm andexpressed by molecular formula TiC_(1-x)N_(x), wherein x is the atomicratio of N to the sum of C and N, and it ranges from 0.45 to 0.95 at topportion and ranges from 0.05 to 0.40 at bottom portion, and (c) Al₂O₃layer having average thickness of 0.5 to 8 μm.

[0030] The average thickness of the hard coating layer is preferably 3to 25 μm, more preferably 5 to 20 μm, and most preferably 7 to 15 μm.Excellent wear resistance cannot be achieved at a thickness of less than3 μm, whereas breakage and chipping at the cutting edge of the cuttingmember easily occur at a thickness of over 25 μm.

[0031] Individual Ti compound layers are believed to ensure sufficientadherence between different two layers. It becomes difficult to keepsufficient adherence at a thickness of less than 0.1 μm, whereas wearresistance decreases at a thickness of over 5 μm. Accordingly, theaverage thickness of individual Ti compound layers independently of oneanother is set to 0.1 to 5 μm, preferably 0.5 to 4.5 μm, more preferably0.75 to 4 μm, more particularly preferably 1 to 3.5 μm, and mostpreferably 1.5 to 3 μm.

[0032] The Al₂O₃ layer is believed to increase wear resistance of hardcoating layer especially for high speed cutting operation because of itssatisfactory properties such as thermal barrier and oxidationresistance. It becomes difficult to achieve enough wear resistance at athickness of less than 0.5 μm, whereas chipping at cutting edge easilybecomes to occur at a thickness of over 8 μm. Accordingly, the averagethickness of the Al₂O₃ layer is set to 0.5 to 8 μm, preferably 0.75 to 7μm, more preferably 1 to 6 μm, more particularly preferably 2 to 5 μm,and most preferably 3 to 4 μm.

[0033] The gradient 1-TiCN layer is believed to improve the toughness ofhard coating layer as noted above. It becomes difficult to providesatisfactory properties of this layer at a thickness of less than 2 μm,whereas wear resistance of this layer decrease sharply at a thickness ofover 15 μm. Accordingly, the average thickness of the gradient 1-TiCNlayer is set to 2 to 15 μm, preferably 2.5 to 12.5 μm, more preferably 3to 10 μm, more particularly preferably 4 to 7 μm, and most preferably 5to 6 μm.

[0034] With regard to the gradient 1-TiCN layer expressed asTiC_(1-x)N_(x), when the x value the at top portion is less than 0.45 orwhen that value at the bottom portion is more than 0.40, theconcentration gradient of C and N becomes rather small, and as aconsequence further improvement of layer toughness cannot be attained.Similarly, when the x value at the top portion is more than 0.95 or whenthat value at bottom portion is less than 0.05, it becomes difficult tosecure its longitudinal crystal structure, and as a consequence thetoughness of the layer decreases sharply, then chipping at the cuttingedge may occur. Accordingly, the x value at top portion is preferablyset to 0.45 to 0.95, more preferably 0.50 to 0.85, and most preferably0.55 to 0.75; and the x value at bottom portion is preferably set to0.05 to 0.40, more preferably 0.10 to 0.35, and most preferably 0.15 to0.30.

[0035] A preferable embodiment is a coated carbide member for a cuttingtool that includes a substrate and a hard coating layer on thesubstrate, wherein the hard coating layer includes (a) at least onetitanium compound layer composed of at least one layer of granulartitanium compound selected from the group including TiC, TiN, TiCN,Ti₂O₃, TiCO, TiNO, TiCNO, and mixtures thereof; (b) 1-TiCN layer havinga compositional gradient of carbon (C) and nitrogen (N) along with itsgrowth direction (gradient 1-TiCN); and (c) Al₂O₃ layer,

[0036] wherein gradient 1-TiCN is expressed by molecular formulaTiC_(1-x)N_(x), wherein x is the atomic ratio of N to the sum of C andN, and it ranges from 0.45 to 0.95 at top portion of the gradient 1-TiCNlayer and ranges from 0.05 to 0.40 at bottom portion thereof.

[0037] Another preferable embodiment of the present invention is toprovide a process for producing a coated carbide member with gradient1-TiCN layer by changing the gas concentration of the reactive gasconcentration of CH₃CN,CH₄, and/or N₂, and the deposition temperature,from 850-950° C. for the bottom portion to 960-1040° C. for the topportion, during the deposition period of 1-TiCN layer.

[0038] Having generally described this invention, a furtherunderstanding can be obtained by reference to certain specific examplesthat are provided herein for purposes of illustration only and are notintended to be limiting unless otherwise specified.

EXAMPLES Example 1

[0039] The following powdered materials were prepared as raw materialsfor substrates: a WC powder with an average grain size of 1.5 μm or 3μm, a (Ti,W)CN powder (TiC/TiN/WC=24/20/56) with an average grain sizeof 1.2 μm, a TaC/NbC powder (TaC/NbC=90/10) with an average grain sizeof 1.3 μm, a Cr₃C₂ powder with an average grain size of 1 μm, a VCpowder with an average grain size of 1.2 μm and Co powder with anaverage grain size of 1.2 μm. Those powders were compounded based on theformulation shown in Table 1, wet-mixed in a ball mill for 72 hours anddried. Several dry powder mixtures were prepared in this manner and theneach was pressed at a pressure of 1 ton/cm² to form green compacts,which were sintered under the following conditions; pressure: 0.001Torr, temperature: 1400 to 1460° C., holding duration: 1 hour, tomanufacture cemented carbide insert substrates A through E defined inISO-CNMG120408 (the entire contents of which are hereby incorporated byreference), whose shape is shown in FIG. 1.

[0040] The cutting edges of the cemented carbide insert substrates Athrough F were honed. Each substrate was subjected to chemical vapordeposition using conventional equipment under the conditions shown inTables 2 and 3 to provide hard coating layers on the substrate.Individual coating layers shown in Table 2 has homogeneous compositionfrom bottom to top of that layer, and every coating layers other than1-TiCN in Table 2 has granular crystal structure. To manufacture coatedcemented carbide inserts in accordance with the present invention andconventional, a hard coating layer was coated on each substrate, whereinthe designed coating layer structure and thickness of each layer isshown in Tables 4, 5. Coated cemented carbide inserts in accordance withthe present invention 1 through 10 and conventional coated carbideinserts 1 through 10 were manufactured in such a manner.

[0041] In Table 4, the description for example this invention 1“1-TiCN(a)˜1-TiCN(2)5 steps, (4.3)” means a gradient 1-TiCN layer of 4.3μm of its aimed thickness which has prepared by following method, thatis, bottom portion of the layer was manufactured using gas condition of1-TiCN (a) in Table 3, top portion of the layer was manufactured usinggas condition of 1-TiCN (2), and there were 5 steps of change in gasconcentration of CH₃CN, CH₄ and/or N₂ during deposition of the layer.Likewise, the description for example this invention 2“1-TiCN(b)˜1-TiCN(1) (continuous), (3.8)” means a gradient 1-TiCN layerof 3.8 μm of its aimed thickness which has prepared by following method,that is, bottom portion of the layer was manufactured using gascondition of 1-TiCN (b) in Table 3, top portion of the layer wasmanufactured using gas condition of 1-TiCN (1), and there was acontinuous change in gas concentration of CH₃CN, and/or N₂ duringdeposition of the layer.

[0042] To investigate the x value at the portion both 0.2 μm from upperinterface and 0.2 μm from lower surface of individual gradual 1-TiCNlayer for coated cemented carbide in ax accordance with presentinvention 1 through 10, a cross-sectional analysis using Auger ElectronSpectroscopy (AES) was performed and it was confirmed that x value ofindividual gradient 1-TiCN layer was almost identical to the designedvalue. From the investigation of the hard coating layers using opticalmicroscope, the thickness of each layer was almost identical to designedthickness.

[0043] Further, for coated cemented carbide inserts of the presentinvention 1 through 10 and conventional coated cemented carbide inserts1 through 10, the following interrupted cutting tests were conducted.The wear width on the flank face was measured in each test. The resultsare shown in Table 6.

[0044] (1-1) Cutting style: Interrupted turning of alloyed steel

[0045] Work piece: JIS SCM440 round bar having 4 longitudinally grooves

[0046] Cutting speed: 300 m/min

[0047] Feed rate: 0.32 mm/rev

[0048] Depth of cut: 5 mm

[0049] Cutting time: 10 min

[0050] Coolant: Dry

[0051] Cutting style: Interrupted turning of alloyed steel

[0052] Work piece: JIS SCM440 round bar having 4 longitudinally grooves

[0053] Cutting speed: 300 m/min

[0054] Feed rate: 0.6 mm/rev

[0055] Depth of cut: 1.5 mm

[0056] Cutting time: 10 min

[0057] Coolant: Dry TABLE I Carbide Composition (wt %) substrate Co (Ti,W) CN (Ta, Nb) C Cr₃C₂ VC WC A 6 — 2 — — Balance (1.5 μm) B 6 6 — 0.10.2 Balance (3.0 μm) C 7 7 5 0.4 — Balance (3.0 μm) D 8 5 4 0.4 0.2Balance (3.0 μm) E 10 — — 0.1 — Balance (1.5 μm)

[0058] TABLE 2 Manufacturing conditions of hard coating layer AmbienceHard coating layer Composition of reactive gas (volume %) Pressure(Torr) Temperature (° C.) TiC TiCl₄:3%, CH₄:4%, H₂:Balance 50 1020 TiN(1st layer) TiCl₄:3%, N₂:40%, H₂:Balance 150 900 TiN (others) TiCl₄:3%,N₂:45%, H₂:Balance 50 1040 1-TiCN TiCl₄:3%, N₂:30%, CH₃CN:1%, H₂:Balance50 900 TiCN TiCl₄:3%, N₂:6%, CH₄:2%, H₂:Balance 120 960 Ti₂O₃ TiCl₄:3%,CO2:2%, H₂:Balance 100 1020 TiCO TiCl₄:3%, CO:2%, CH₄:2%, H₂:Balance 1001000 TiNO TiCl₄:3%, N₂:30%, CO:2%, H₂:Balance 120 1000 TiCNO TiCl₄:3%,CO:2%, CH₄:2%, N₂:30%, H₂:Balance 120 1000 α-Al₂O₃ AlCl₃:5%, CO₂:8%,HCl:1.5%, H₂S:0.5%, H₂:Balance 50 1000 κ-Al₂O₃ AlCl₃:5%, CO₂:6%,HCl:1.5%, H₂S:0.3%, H₂:Balance 50 950

[0059] TABLE 3 Manufactuzing conditions of gradient 1-TiCN layer1-TiCl-xNx layer Composition of reactive gas (volume %) pressure(kPa)temperature(° C.) upper portion 1-TiCN (1) (x:0.45) TiCl₄:2%, N₂:30%,CH₄:1%, CH₃CN:0.6%, H₂:Balance 8.0 980 1-TiCN (2) (x:0.55) TiCl₄:2%,N₂:30%, CH₄:0.6%, CH₃CN:0.4%, H₂:Balance 8.0 980 1-TiCN (3) (x:0.65)TiCl₄:2%, N₂:35%, CH₄:0.3%, CH₃CN:0.4%, H₂:Balance 8.0 980 1-TiCN (4)(x:0.75) TiCl₄:2%, N₂:35%, CH₄:0.1%, CH₃CN:0.2%, H₂:Balance 8.0 9801-TiCN (5) (x:0.85) TiCl₄:2%, N₂:40%, CH₃CN:0.2%, H₂:Balance 8.0 9801-TiCN (6) (x:0.95) TiCl₄:2%, N₂:40%, CH₃CN:0.05%, H₂:Balance 8.0 980lower portion 1-TiCN (a) (x:0.05) TiCl₄:2%, CH₄:3%, CH₃CN:0.2%,H₂:Balance 8.0 930 1-TiCN (b) (x:0.10) TiCl₄:2%, CH₄:2%, CH₃CN:0,4%,H₂:Balance 8.0 930 1-TiCN (d) (x:0.20) TiCl₄:2%, N₂:5%, CH₄:1%,CH₃CN:1%, H₂:Balance 8.0 930 1-TiCN (t) (x:0.30) TiCl₄:2%, N₂:5%,CH₃CN:1%, H₂:Balance 8.0 930 1-TiCN (g) (x:0.35) TiCl₄:2%, N₂:10%,CH₃CN:1%, H₂:Balance 8.0 930 1-TiCN (g) (x:0.40) TiCl₄:2%, N₂:10%,CH₃CN:0.8%, H₂:Balance 8.0 930

[0060] TABLE 4 Sub- Hard coating layer (Figure in parenthesis meansdesigned thickness; μm) Insert strate First layer Second layer Thirdlayer Forth layer Fifth layer Sixth layer This 1 A TiN (0.3) TiCN (1.5)1-TiCN (a) ˜ 1-TiCN (2) α-Al₂O₃ (0.6) TiN (0.3) — inven- [5 steps],(4.3) tion 2 B TiC (0.4) TiN (0.7) 1-TiCN (b) ˜ 1-TiCN (1) TiCO (0.5)κ-Al₂O₃ (7.8) — [continuous], (3.8) 3 B TiN (0.5) 1-TiCN (c) ˜ 1-TiCN(5) TiCNO (0.6) α-Al₂O₃ (1.8) TiN (0.4) — [3 steps], (4.0) 4 C TiC (0.5)1-TiCN (c) ˜ 1-TiCN (3) TiC (1.5) κ-Al₂O₃ (3.7) α-Al₂O₃ (2.4) TiN (0.5)[continuous], (7.2) 5 C TiN (0.5) 1-TiCN (d) ˜ 1-TiCN (4) TiCN (0.6)TiCN (3.6) κ-Al₂O₃ (2.2) TiN (0.4) [15 steps], (9.4) 6 D TiN (0.9)1-TiCN (d) ˜ 1-TiCN (3) TiC (0.5) TiCNO (0.3) α-Al₂O₃ (2.6) — [2 steps],(8.5) 7 D TiN (0.6) 1-TiCN (e) ˜ 1-TiCN (2) TiC (2.7) TiCNO (0.5)α-Al₂O₃ (1.4) TiN (0.4) [continuous], (2.1) 8 E 1-TiCN (e) ˜ 1-TiCN (4)1-TiCN (e) ˜ 1-TiCN (4) Ti₂O₃ (0.5) κ-Al₂O₃ (3.2) TiCO (0.2) TiN (0.4)[continuous], (6.6) [continuous], (6.6) 9 E TiC (1.0) 1-TiCN (1) ˜1-TiCN (5) α-Al₂O₃ (1.6) TiCO (0.2) TiCO (0.2) — [10 steps], (12.0) 10 FTiC (1.2) TiCNO (0.7) 1-TiCN (1) ˜ 1-TiCN (6) TiNO (0.5) α-Al₂O₃ (3.4)κ-Al₂O₃ (2.9) [continuous], (14.5)

[0061] TABLE 5 Hard coating layer (Figure in parenthesis means designedthickness; μm) Insert Substrate First layer Second layer Third layerForth layer Fifth layer Sixth layer Conventional 1 A TiN (0.3) TiCN(1.5) 1-TiCN (4.3) α-Al₂O₃ (0.6) TiN (0.3) — 2 B TiC (0.4) TiN (0.7)1-TiCN (3.8) TiCO (0.5) κ-Al₂O₃ (7.9) — 3 B TiN (0.5) 1-TiCN (4.0) TiCNO(0.6) α-Al₂O₃ (1.8) TiN (0.4) — 4 C TiC (0.5) 1-TiCN (7.2) TiC (1.5)κ-Al₂O₃ (3.7) α-Al₂O₃ (2.4) TiN (0.5) 5 C TiN (0.5) 1-TiCN (9.4) TiN(0.6) TiCN (3.6) κ-Al₂O₃ (2.2) TiN (0.4) 6 D TiN (0.9) 1-TiCN (8.5) TiC(0.5) TiCNO (0.3) α-Al₂O₃ (2.6) — 7 D TiN (0.6) 1-TiCN (2.1) TiC (2.7)TiCNO (0.5) α-Al₂O₃ (1.4) TiN (0.4) 8 E 1-TiCN (6.6) TiC (3.5)Ti₂O_(3 (0.5)) κ-Al₂O₃ (3.2) TiC (0.2) TiN (0.3) 9 E TiC (1.0) 1-TiCN(12.0) α-Al₂O₃ (1.6) TiCO (0.2) TiN (0.4) — 10 F TiC (1.2) TiCNO (0.7)1-TiCN (14.5) TiNO (0.5) α-Al₂O₃ (3.4) κ-Al₂O₃ (2.9)

[0062] TABLE 6 Flank wear (mm) Flank wear (mm) high speed and high speedand high speed and high speed and Insert thick depth-of-cut high feedInsert thick depth-of-cut high feed This invention 1 0.23 0.25Conventional 1 Failure at 1 min. Failure at 1 min. 2 0.25 0.28 2 Failureat 1.5 min. Failure at 2 min. 3 0.22 0.21 3 Failure at 2.5 min. Failureat 2 min. 4 0.18 0.19 4 Failure at 3 min. Failure at 2.5 min. 5 0.140.15 5 Failure at 3.5 min. Failure at 3 min. 6 0.15 0.14 6 Failure at 3min. Failure at 3.5 min. 7 0.20 0.21 7 Failure at 1 min. Failure at 1min. 8 0.18 0.18 8 Failure at 2.5 min. Failure at 3 min. 9 0.25 0.27 9Failure at 2 min. Failure at 1.5 min. 10 0.28 0.30 10 Failure at 0.5min. Failure at 1.5 min.

[0063] Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A coated cemented carbide cutting tool member, comprising: asubstrate and a hard coating layer deposited on said substrate, whereinsaid hard coating layer has an average thickness of 3 to 25 μm andcomprises: (1) at least one layer having an average thickness of 0.1 to5 μm and comprising a granular Ti compound selected from the groupconsisting of TiC, TiN, TiCN, Ti₂O₃, TiCO, TiNO, TiCNO and mixturesthereof; (2) a TiCN layer having an average thickness is 2 to 15 μm andcomprising a longitudinal growth crystal structure; and (3) an Al₂O₃layer having an average thickness of 0.5 to 8 μm; wherein said TiCNlayer comprises a growth direction and a compositional gradient ofcarbon and nitrogen along said growth direction.
 2. The coated cementedcarbide cutting tool member according to claim 1, wherein thecomposition of said TiCN layer is TiC_(1-x)N_(x) wherein the x value atan upper portion of said TiCN layer is in the range of 0.45 to 0.95, andthe x value at a lower portion of said TiCN layer is in the range of0.05 to 0.40.
 3. The coated cemented carbide cutting tool memberaccording to claim 2, wherein said upper and lower portions are withrespect to the surface of said substrate.
 4. The coated cemented carbidecutting tool member according to claim 1, wherein said TiCN having alongitudinal growth crystal structure is 1-TiCN.
 5. The coated cementedcarbide cutting tool member according to claim 1, wherein saidcompositional gradient in said TiCN layer varies stepwise.
 6. The coatedcemented carbide cutting tool member according to claim 1, wherein saidcompositional gradient in said TiCN layer varies continuously.
 7. Thecoated cemented carbide cutting tool member according to claim 1,wherein said Al₂O₃ layer comprises at least one selected from the groupconsisting of α-Al₂O₃,κ-Al₂O₃, and mixtures thereof.
 8. A process forproducing a coated carbide member, comprising: depositing a TiCN layerwith a reactive gas, said layer having a lower portion and an upperportion; and during said depositing, changing a concentration in saidreactive gas of at least one selected from the group consisting ofCH₃CN,CH₄,N₂, and mixtures thereof; wherein said depositing of saidlower portion is carried out at a deposition temperature of 850-950° C.,and said depositing of said upper portion is carried out at a depositiontemperature of 960-1040° C.
 9. The process according to claim 8, whereinsaid changing is stepwise.
 10. The process according to claim 8, whereinsaid changing is continuous.
 11. The process according to claim 8,further comprising depositing at least one layer having an averagethickness of 0.1to 5 μm and comprising a granular Ti compound selectedfrom the group consisting of TiC, TiN, TiCN, Ti₂O₃, TiCO, TiNO, TiCNOand mixtures thereof.
 12. The process according to claim 8, furthercomprising depositing at least one Al₂O₃ layer having an averagethickness of 0.5 to 8 μm.
 13. The process according to claim 8, whereinsaid TiCN layer has an average thickness of 2 to 15 μm and comprises alongitudinal growth crystal structure.
 14. The process according toclaim 8, wherein said TiCN layer comprises a growth direction and acompositional gradient of carbon and nitrogen along said growthdirection.
 15. The process according to claim 8, wherein the compositionof said TiCN layer is TiC_(1-x)N_(x), and wherein the x value at saidupper portion is in the range of 0.45 to 0.95, and the x value at saidlower portion is in the range of 0.05 to 0.40.
 16. The process accordingto claim 8, wherein said upper and lower portions are with respect tothe surface of said substrate.
 17. The process according to claim 8,wherein said TiCN is 1-TiCN.
 18. A coated carbide member, produced bythe process according to claim 8.